Production of yarns



p. WILSONI PRODUCTION or nmxs3 Sept 8 19701 F11ed.Jan. 6, 1969 United States Patent 3,527,045 PRODUCTION OF YARNS Davd Wilson, West Bridgforfl, England, assignor to Clutsom-Penn Intemafional Limted, Coalvlle, Leicester, England, a British company Filed Jan. 6, 1969, Ser. No. 789,119 Claims priority, application Great Britain, Jan. 30, 1968,

4,774/68 Int. Cl. D02g 3/32; D02j 13/00 U.S. Cl. 57-152 7 Claims ABSTRACT OF THE DISCLOSRE of a covering operation on the bare yarn, although it may be carried out when winding the initially bare yarn trom one package to another.

This invention relates to the production of thermoplastic elastomeric yarns (which term includes threads) of the class containing at least 85% segmented polyurethane. Such yarns are generally known, and will for convenience hereinafter be referred to, as Spandex yarns.

It is already known to heat set cvered or core spun Spandex yarns with the aim of stabilising their stretch properties.

Moreover, a process has previously been proposed on British patent specfication No. 916,287 for permanenfly altering the dimensions of, inter alia, threads of a synthetc elastomerc polymer, said process comprising exposing the threads to a temperature of at least 100 C. while they are stretched and cooling the threads to a temper ture below 70 C. while they are still under tension. In this previously proposed process the time of treatment at the elevated temperature must be suflficiently long to cause the thread to retain a substantal proportion of the stretch, the minimum treating time being minutes but the preferred time being from about 15 to 60 minutes.

Another previously proposed process described in British specificafion No. 1,103,485 aims to increase the tensile strength and modulus of elastomeric threads (having an elongation at break Of at least 150%, a tensile recovery of 90% or more and a stress decay of less than 30%) in a comparatively short time, this further process con sisting in heating a synthetic elastomeric thread to a temperature of at least 130 C. and simultaneously stretching it from ZOO-600 percent while it is passing between two thread-storage devices the speeds of which are adjusted to give the desired degree of stretchjng over a period of time not exceeding 1 minute, the thread leaving the second storage device being allowed to relax freely and being collected in a form substantially free from ten sron.

The general aim of the present invention is to provide an improved process for producing Spandex yarns Patented Sept. 8, 1970 whereby advantages, hereinafter to be specified, are derived over and above those secured from the adoption of known processes.

A particular object of the invention is to produce spandex yarns of deniers or c0unts not at present commercially available.

Another specific object is to produce spandex yarns having improved properties in relation to those et comparable standard products.

The process of this invention consists in simultaneously extending bare spandex yarn to an extent of less than 200 percent and heat setting it at a temperature in the range l60300 C. over a period of time no greater than 30 seconds.

According to a feature of the process of this invention, the percentage of the extension and the degree temperature to which the spandex yarn is subjected may be so judiciously controlled within the specified ranges as to impart desired propertes to the yarn. Thus, under certain conditions, predetermined by experiment, some properties such, for example, as breaking elongation may be found to be superior to those of the standard product.

Advantageously, the bare spandex yarn may be extended whilst it is being caused to run over or past, and preferably in contact with an electrically heated plate. In this connection a heater plate such as is used in a false twisting process may be employed.

In accordance with an important aspect of the present invention, the process already broadly defined herein may be actually carried out on a covering machine, that is to say a machine for applying spirally upon initially bare spandex a covering thread or threads.

But although the process of this invention is particularly suitable for carrying out on a covering machine, there is no limitation in this respect since it may also be carried out as, say, part of a winding operation, e.g. when winding bare spandex yarn from one package such as a cheese to another such as a warp beam.

In order that the invention may be more clearly understood and readily carried into practical efiect, one form of apparatus for performance of the improved process on a covering machine will now be described with reference to the accompanying drawing of which the single figure shows a layout of the said apparatus in a purely diagrammatic fashion.

Referring to the drawing it will be seen that a bare spandex yarn Y is being drawn from a supply package 1 and finally wound up on to a take-up package 2. The covering machine, in the illustrated example, comprises two covering spindles 3 and 4 which support =bobbins 5 and 6 of covering threads. The bare spandex yarn Y runs freely right through the spindles 3 and 4, and the latter and hence also the bobbins 5 and 6 supported thereby are spaced apart axially in, and arranged to rotate about, a straight upward portion of the path of travel of the said yamindicated by the arrows.

The apparatus is equipped, in advance of the covering bobbins 5 and 6, with both means for extending, i.e. stretching, the travelling bare yarn Y and also a heater 7 through which the extended yarn is guided. The heater, in box form, incorporates an electrically heated plate 7 over which the yarn travels in contact therewith.

In the specific apparatus illustrated there are provide first and second feed wheels 8 and 9 respectively -around which the bare yarn Y is passed, the second wheel 9 being caused to run appropriately faster than the first to extend the yarn, and the heater 7 being located between the said two wheels so that the initially bare yarn becomes heat set prior to being covered. In this arrangement the two feed wheels 8 and 9, spaced apart with the heater between them, are located after the supply package 1 and immediately before the first rotoary covering spindle 3.

Alternatively, the feed wheel 8 may be dispensed with, in which instance extension of the bare spandex may be etfected by driving the supply package 1 more slowly than the then single feed wheel 9.

In any event, the apparatus may advantageonsly include a takeup roller 10, and a reciprocatory guide 11 which is movable to and fro parallel to the axis of the take-up package 2 for the purpose of laying the extended and heat set and now covered yarn evenly upon the said package.

It will be seen that the yarn Y travels generally in an upward direction from the supply package 1 to the takeup package 2, with the exception that it travels horizontally through the heater 7, although there are no limitations in these respects.

As previously mentioned, under preferred conditions of extension and temperature, an increase in breaking elonga tien of the resultant yarn can be obtained, which is of particular importance in the covering operation, as it enables a higher draft than heretofre to be used in the covering zone. For example, the following figures are obtainable with a particular commercial spandex yarn of 1120 denier, when running at 100% extension over an electrically heated metal plate, 12" in length at a takeup speed of 20 ft./minute so that the bare yarn is simultaneously extended and heat set over a period of 3 seconds only:

Breaking Plate temperature (measured by elongation (percent) thermophil temperature probe) Untreated 550 230 C. 550 245 C. 600 250 C. 700 255 C. 750

Similarly, another type of commercial spandex yarn of 840 denier, treated under the same conditions, gives the following results:

Breaking Temperature: elongation Untreated 550 215 C. 600 225 C. 700 230 C. 750 240 C 800 Pereentage et extension retained on Percentage et the set Temperature of which is permanent treatment C.) relcasing (percent set) to a bail 011 1,120 denier:

Of the heat-setting temperatures specified in the foregoing tables, the preferred ones are 255 C. for the 1120 denier yarn; and 230 C. for the 840 denier yarn.

Fine deniers of covered spandex yarn can -be produced by the herein described process. For example, starting from 20 denier bare spandex (the finest spandex currently commercially available is 20 denier), it is possible to produce a covered 10 denier spandex yarn. Also by the adaption of this invention, covered spandex yarns of substantially heavier deniers not at prescrit commercially available can be produced. Thus, for instance starting from 1120 denier bare spandex it is possible to produce a covered 650 denier spandex yarn.

I claim:

1. A process for the production of thermoplastic clastomeric yarn containing at least 85% segmented polyurethane in which the yarn is simultaneously extended and heated over a short period of time, characterised in that the yarn, in a bare condition, is simultaneously extended to an extent of less than 200 percent and heat set at a temperature in the range 160300 C. over a period of time net exceeding 30 seconds.

2. A process according to claim 1, which is carried out on a covering machine as part of a covering operation on the initially bare yarn.

3. A process according to claim 1, which is carried out as part of a winding operation.

4. A process according to claim 1, wherein the bare yarn is treated in conditions of extension and temperature selected to produce increased breaking elongation.

S. A process according to claim 1, wherein the bare yarn is heated by running it in contact with an electrically heated plate.

6. A process according to claim 1, wherein the bare yarn is extended to an extent of or approximately 50.

7. A thermoplastic elastomeric yarn made according to the process of claim 1.

References Cited UNITED STATES PATENTS 3,115,745 12/1963 Lathem et al. 57163 3,243,950 4/1966 Hermes 57163 3,342,028 9/1967 Matsubayashi et al. 57163 3,349,458 10/1967 Mainz 57152 XR 3,357,076 12/1967 Greenwald et al. 57152 XR 3,387,451 6/1968 Cape et al 57152 XR 3,387,448 6/1968 Lathem et al 57152 5 DONALD E. WATKINS, Primary Examiner U.S. Cl. X.R. 57-34, 163 

